The exemplary embodiments described herein relate to nonvolatile memory devices, and more particularly, to NAND type flash memory devices of a three-dimensional structure having a high degree of integration.
Generally, nonvolatile memory devices can electrically erase data and electrically store data. Nonvolatile memory devices can also retain their stored data when their power supplies are interrupted. Recently, nonvolatile memory devices have been widely used in various fields.
Nonvolatile memory devices include memory cell transistors of various types and may be classified into a NAND type and a NOR type according to a cell array structure in the devices. NAND type nonvolatile memory devices and NOR type nonvolatile memory devices have advantages of high integration and high speed, respectively.
Since a NAND type nonvolatile memory device has a cell string structure connecting a plurality of memory cells in series, they are conducive to high integration. Also, since a NAND type nonvolatile memory device adopts an operation method of simultaneously changing data stored in a plurality of memory cells, a speed of updating data is very high compared with a NOR type nonvolatile memory device. NAND type nonvolatile memory devices are mainly used in portable electronic devices requiring a mass storage such as a digital camera or a MP3 player because of high integration and high update speed.
A NAND type nonvolatile memory device of a three-dimensional structure is being developed.